The present invention relates to a cleaner for a toner fixing device in an electrophotographic printer or the like.
In a toner fixing device of the thermal type, paper to which a toner image adheres due to electrostatic force or the like is moved through the nip of a pair of heated fixing rollers whereby the toner image is fused to the paper. Normally, the surface of at least one of the fixing rollers is coated with a fluorine resin or the like, and a separating agent such as silicone oil is applied to the coating material to prevent the toner image from adhering to the fixing roller. However, in actuality a very small quantity of toner will usually remain on fixing roller. To remove such remaining toner from the fixing roller, a cleaning member is usually placed in contact with the roller.
FIG. 1 shows a conventional cleaner for a toner fixing device. Paper 10 is conveyed on paper guides 8 and 9 so that a toner image is fixed to the paper by a pair of fixing rollers composed of a heated roller 3 and a backup roller 7. A piece of felt 11 is positioned to contact the heated roller 3 to wipe away excess toner remaining on the roller 3. In this arrangement, however, it is necessary to frequency replace the felt. In other words, there is a disadvantage that the maintenance interval of the machine is short.
FIG. 2 shows another conventional cleaner for a toner fixing device. In this case, a cleaning member 12 composed of felt or other material is supplied from a roll, and the contaminated portion of a cleaning member 12 so formed is gradually wound up. The maintenance interval of the machine is thus increased. However, since there is a large distance between the supply and take-up rolls for the cleaning member, there is a disadvantage that the size of the cleaner is large. Moreover, since a device for regulating the speed of movement of the cleaning member 12 and an arrangement for detecting the quantity of the unused portion of the cleaning member need be provided, there is another disadvantage in that the construction of the cleaner is complicated.
FIG. 3 shows a cleaner disclosed in Japanese Utility Model Application (OPI) No. 112261/84. In this cleaner, an endless belt of felt 1 is tightly engaged between a drive shaft 13 and guide shafts 14. Although this cleaner has the advantage that the period of use of the felt 1 is long, the cleaner nevertheless has the disadvantage that the cleaner felt requires a relatively large space, and it is difficult to arrange the felt in the very narrow space available around the fixing roller.
FIG. 4 shows a cleaner of a type disclosed in Japanese Patent Application No. 13989/79. In this case, the cleaner is provided for a photosensitive body 16. A cleaning member 18 is made of a thin sheet of a material such as paper and a film. Since the rigidity of the thin sheet is low, it is difficult to neatly fold the thin sheet into a retrieval chamber 20 with a drive roller 17, and the thin sheet is likely to crinkle. For these reasons, the cleaning member 18 is likely to be skewed if it is circulated more than once. Hence, this cleaner has the disadvantage that the cleaning member can be used only once.
Moreover, silicone oil is always present between the cleaning member 18 and the fixing roller, reducing the coefficient of friction on the surface of the cleaning member. For that reason, there is a problem that it is difficult to stably drive the cleaning member with a single drive roller. The conventional cleaner shown in FIG. 3 has the same problem.